Anodizing of Pure Magnesium in Sodium Hydroxide Electrolyte Solution

A protective composite coating on an AZ31B magnesium alloy was prepared by anodic oxidation to form an oxide layer, followed by single immersion in maleic anhydride-g-liquid polybutadiene (MALPB) solution to cover a polymer coating on top. As a low-molecular weight polymer with low viscosity, MALPB had a tendency to infiltrate into the pores and cracks in the anodic layer to fill the defects among oxides so that a compact layer could be formed after it was cured by its hardeners, as observed by scanning electron microscopy (SEM). This compact layer, which was composed of anodic oxides integrated with solidified MALPB, possessed thickness around 0.7 μm as detected by energy dispersive X-ray (EDX). The anodized, MALPB-coated AZ31B alloy exhibited enhancement in corrosion resistance superior to that separately coated by anodizing oxides or MALPB, as reflected by its much higher corrosion potentials (E ccor) and lower corrosion current density (i corr) in DC polarization tests. Based on electrochemical impedance spectroscopy (EIS) data, we conclude that the anticorrosive performance of the composite coating can be attributed to the barrier effects provided by different layers when the electrolyte passed through the MALPB layer, compact layer, and then the inner anodic layer before it reached the surface of Mg alloy, and that among them, the compact layer acted as a much more effective barrier to the electrolyte. The appearance of damaged areas on the composite coating surface after a much longer duration in a salt spray environment revealed that the life-span of the AZ31B Mg alloy could be greatly prolonged if the pores and cracks on the anodizing films were properly sealed by suitable polymers.

Anodic layers have been grown on 304L stainless steel (304L SS) using two kinds of fluoride-free organic electrolytes. The replacement of NH4F for NaAlO2 or Na2SiO3 in the glycerol solution and the influence of the H2O concentration have been examined. The obtained anodic layers were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and potentiodynamic polarization tests. Here, it was found that, although the anodic layers fabricated within the NaAlO2-electrolyte and high H2O concentrations presented limited adherence to the substrate, the anodizing in the Na2SiO3-electrolyte and low H2O concentrations allowed the growth oxide layers, and even a type of ordered morphology was observed. Furthermore, the electrochemical tests in chloride solution determined low chemical stability and active behavior of oxide layers grown in NaAlO2-electrolyte. In contrast, the corrosion resistance was improved approximately one order of magnitude compared to the non-anodized 304L SS substrate for the anodizing treatment in glycerol, 0.05 M Na2SiO3, and 1.7 vol% H2O at 20 mA/cm2 for 6 min. Thus, this anodizing condition offers insight into the sustainable growth of oxide layers with potential anti-corrosion properties.

Ellipsometric changes produced by oxidation—reduction potential cycles applied to cadmium in sodium hydroxide solutions

Characterization of the hard anodizing layers formed on 2014-T3 Al alloy, in sulphuric acid electrolyte containing sodium lignin sulphonate

This article focuses on the development of the anode layer for solid oxide fuel cells by plasma spraying. The composite (cermet) anode, developed by thermal spraying, consisted of nickel and yttria-stabilized zirconia (YSZ). The effect of different plasma-spraying technologies on the microstructure characteristics and the electrochemical behavior of the anode layer were investigated. Coatings were fabricated by spraying nickel-coated graphite or nickel oxide with YSZ using a Triplex II plasma torch under atmospheric conditions as well as a standard F4 torch under atmospheric or soft-vacuum conditions. The investigations were directed to have an open microporous structure, higher electrical conductivity, and catalytic activity of anode deposits. Porosity was investigated by measuring the gas permeability. Scanning electron microscopy and x-ray diffraction technologies were applied to examine the morphology, microstructure, and composition of the layers. Electrical conductivity measurements were carried out to determine the ohmic losses within the anode layer. The most promising layers were analyzed by measuring the electrochemical behavior to obtain information about catalytic activity and performance.

Electrochemical behavior of rolled Pb–0.8%Ag anodes in an acidic zinc sulfate electrolyte solution containing Cl− ions

The availability of a wide array of colloidal organic/inorganic nanostructures has opened up an interface to establish highly innovative and attractive hybrid materials for a number of optoelectronic applications recently. In this regard, a colloidal route has been established to fabricate hybrid photodiodes and study the influence of Ni1−xCoxO colloids as anodic buffer layers in them. The buffer oxide nanostructures were established through a facile surfactant free wet chemical approach with a cubic phase. Their absorbance properties were found to be influenced by the charge transfer process taking place between the O2− and Co2+ ions, while the vibrations corresponding to Co ions in between the tetrahedral and octahedral sites were found to be predominant in the Raman spectroscopy measurements. Hybrid p–n junctions were fabricated over the chemically in situ polymerized polypyrrole deposits using n-Zn1−yInyO and p-Ni1−xCoxO colloidal nanostructures through a drop casting methodology. The structural properties and distribution of the hybrid nanostructures across the heterostructures were perceived through Raman and scanning electron microscopy. The electrical properties of the fabricated hybrid heterostructures were assimilated using I–V characteristics, which revealed the interfacial anodic buffer layers to improve the charge selectivity across the corresponding electrodes by acting as efficient hole transporting layers (HTL) and blocking the flow of electrons.

Tartaric–sulfuric acid (TSA) anodizing is an electrochemical process used for generating an anodic layer on the surface of aluminum alloys for aerospace applications. It must provide corrosion resistance and ensure no detrimental effect on the required fatigue properties for structural applications. This work aimed at analyzing the properties of the anodic layer and evaluating its influence on the fatigue behavior of the AA 7050‐T7451. The film properties were analyzed using optical and scanning electron microscopies. The surface residual stress (SRS) field in the as‐machined and anodized conditions was evaluated by the X‐ray diffraction technique.The results showed that TSA induces an appreciable reduction in the fatigue life, especially at lower values of stress amplitude, due to the presence of defects at the interface between the substrate and the anodic film. No correlation was observed between the presence of the anodic layer and the development of a tensile SRS field.

Direct Methanol Fuel Cells (DMFCs) offer advantages from quick refills to the elimination of recharge times. They show the most potential in efficient chemical to electrical energy conversion, but currently one major source of inefficiency within the DMFC system is the electrolyte allowing fuel to cross over from the anode to cathode. Proprietary DuPont™ Nafion® 117 has been the standard polymer electrolyte thus far for all meso-scale direct methanol power conversion systems, and its shortcomings consist primarily of slow anodic reaction rates and fuel crossover resulting in lower voltage generation or mixed potential. Porous Silicon (P-Si) is traditionally used in photovoltaic and photoluminescence applications but rarely used as a mechanical filter or membrane. This research deals with investigations into using P-Si as a functioning electrolyte to transfer ions from the anode to cathode of a DMFC and the consequences of stacking multiple layers of anodes. Porous silicon was fabricated in a standard Teflon cylindrical cell by an anodization process which varied the current density to etch and electro-polish the silicon membrane. The result was a porous silicon membrane with approximately 1.5 μm pore sizes when optically characterized by a scanning electron microscope. The porous membranes were then coated in approximately 0.2 mg/cm2 Pt-Ru catalyst with a 10% Nafion® solution binding agent onto the anode. Voltage versus current data shows an open circuit voltage (OCV) of 0.25V was achieved with one layer when operating at 20°C. When adding a second porous silicon layer, the OCV was raised to approximately 0.32V under the same conditions. The experimental data suggested that the current collected also increased with an additional identical layer of anode prepared the same way. The single difference was that the air cathode side was surface treated with 0.1 mg of Pt black catalyst combined with a 10% Nafion® binding agent to aid in the recombination of hydrogen atoms to form the water byproduct. Porous silicon endurance runs with 2ml of 3% by volume methanol (0.7425M) fuel dissolved in water showed an operating voltage was generated for approximately 3 hours before the level dropped to approximately 65% of the 0.25V maximum voltage. Endurance runs with a second layer added extended the useful cell life to approximately 5 hours under the same conditions. In an effort to quantify these layering results, Fourier Transform Infrared Spectrometry was conducted on a number of samples to verify decreased methanol concentration present in the second layer.

Lithium phosphorous oxynitride as a passive layer for anodes in lithium secondary batteries

Anodizing of 304L stainless steel performed in ethylene glycol solution containing 0.1 M NH4F and 0.1 M H2O at constant voltage under static conditions at 5 °C results in the formation of porous anodic films. Several analysis techniques revealed a rather complex composition of the anodic layer for stainless steel compared to that reported in the literature for iron in the same anodizing conditions. Contrary to what might be expected, the anodic layers consist mainly of iron and chromium fluorides rather than oxides. Furthermore, the multilayer fitting of the Rutherford Backscattered spectroscopy shows a decreasing content of chromium and nickel fluorides from the outermost layer to the innermost layer at the metal/film interface, which is composed only of iron fluoride. Film-assisted dissolution mechanisms and the Gibbs-free energy appear to be responsible for the cation distribution and compounds formed throughout the anodic film. In addition, the thickness and final composition of the anodic layer appear to be dependent on the cleaning process carried out after the anodizing.Graphical abstract

In this study, the effects of two fuel types, i.e., hydrogen and methane on the electrochemical performance of the co-extruded triple layer hollow fiber, were systemically studied. The triple layer hollow fiber consisted of electrolyte/active functional layer (AFL)/anode was fabricated by single-step phase-inversion-based co-extrusion technique prior to the sintering process at temperature range of 1400 to 1500 °C. The hollow fibers were characterized by three-point bending test, gas tightness test, and scanning electron microscope (SEM). The electrochemical performance test was carried out at temperatures of 700–800 °C by flowing fuel at 20 ml/min. Based on the results attained, the gas tightness and bending test are improved by the increase of sintering temperature. SEM results show that the finger-like morphology length around 100 μm is obtained. In addition, the AFL layer located in the middle layer of the hollow fiber has its own finger like which forms sandwich-like structure with the anode layer. The open circuit voltage is recorded at 1.05 V with the highest power density obtained at 0.6 W cm−2 by using hydrogen. By changing the fuel into methane gas, the highest power density is achieved at 0.8 W cm−2. This is due to the methane that carries more hydrogen molecule. This indicates that the methane fuel can be utilized in hollow fiber SOFC systems.

Optimization of mechanical and chemical properties of sulphuric anodized aluminium using statistical experimental methods

Long-term performance of anode-supported SOFC integrated with metal interconnect by joining process

Tribo-mechanical characterization of rough, porous and bioactive Ti anodic layers